Different Cooling Options for Desktop PC

[neve2009]

What do you guys know about passive CPU cooling? My idea is to cool Mobo, CPU, and GPX card without fans or water... but using something like a heatpipe that gets heatsunk to the chassis itself for convection cooling. The CPU won't be overclocked or anything like that.

What do you all know about silent cooling?

Any and all feedback appreciated. Thanks!

[tesco]

I only have experience with passive cooling on my graphics card. I have the Arctic Cooling Accelero.
http://www.arctic.ac/en/p/detail?sArticle=24.%3F
A (http://www.arctic.ac/en/p/detail?sArticle=24.%3F)fter installing I got much better temps than the stock cooler gave me. My card is only an 8800gt though...
The thing is huge though, keep that in mind, I almost couldn't fit it into my case, had to rearrange my hard drives because it blocks one or two slots.

[clocker]

Zalman made (and maybe still does) a totally passive (including the PSU) case, cooled with heatpipes run to aluminum extrusions.
It was absurdly expensive and only allowed for the specific motherboard for which it was designed, so I doubt many were sold.

Passive cooling the motherboard/CPU wouldn't be terribly difficult, depending on the processor.
Just keep the OEM chipset sinks and slap a Scythe Orichi(?) on the processor and you'd probably be fine.
Video is the potential problem.
Video cards sit awkwardly in the slot (upside down and horizontal) and can generate a lot of calories...not sure how you'd deal with that.

[Artemis]

I have alot of experience with Home Theater PC builds and passive cooling as others have said really depends on the components.There are two factors to consider here however, the first is that with an average ambient noise level of 30db in your average home you do not need absolutely silent cooling, you need quiet cooling, and a big fan turning slowly displaces more air than a small fan whirring fast.
The second factor is the TDP of the CPU, passive cooling is only really effective up to a TDP of 65w so a quadcore processor with passive cooling unless it is a truly massive radiator will cook itself. There are tower configured passive radiators (Tuniq is a brand that springs to mind) that can dissipate more heat and are designed for high powered CPU's, but then the second part of the cooling equation, the GPU (graphics card) kicks into the equation. Anything decent has at least one fan if not more mounted on it, which tends to negate the totally silent cooling theory. This is of course if you are using a discrete video card instead of onboard/on processor cards. There are smaller graphics cards which have passive heatsinks mounted, but these are usually used in Home Theater installations.
One of the closest to silent solutions I have dealt with are Arctic Cooling fan/heatsink combinations. They are designed to minimise vibration from the fans and are below the ambient noise level even when running near full-speed so would be worth a look.
If you could give us an idea of the specs of the PC and more importantly it's intended uses then maybe we can help you further.

[clocker]

with an average ambient noise level of 30db in your average home you do not need absolutely silent cooling, you need quiet cooling, and a big fan turning slowly displaces more air than a small fan whirring fast.

An excellent point, worth expanding upon.
The "silent computing" movement thrived because older PCs were horrible noise generators...everything ran hot and the largest fan commonly available was 80mm, 40mm was a common size on chipsets and vid cards.
Because these small fans were deployed against massive heat loads, they ran full speed most of the time and made a shitton of noise.
However, remove the tiny fans and computers STILL made a racket...tiny IDE (or even worse, SCSI) drives make an astounding amount of noise, especially when hardmounted into a flimsy case.
Floppies and CD drives were just as bad but ran less frequently, so their contribution is usually overlooked.

Fortunately, things have changed...new SATA drives- and drive mounting variations- are far quieter than older drives and solid states are completely silent (the quest for a quiet computer will not be cheap!).
You don't even need optical drives anymore, flash media is a viable, and silent, option.
Processors run much cooler and motherboards now come slathered in heatsinks (of questionable utility, but still) and the days of blazing hot Athlons/Pentiums are long gone.

Of course, all is not totally rosy...as Artemis points out, the platforms became more efficient and inherently cooler but the video cards became more power hungry.
These days, when speccing a PC meant to feature video performance you start with the vid card and then make sure everything else can support it, which is 180° different than the old days when processor/RAM was the critical consideration.
This means that your cooling attention must change focus as well, the vid card(s) are your most active heat source these days.

When considering your cooling approach, the first axiom you must embrace is: "You have no idea what temperature your components are running".
Unless you've invested in some fairly expensive and sophisticated equipment, you're relying on sensors of dubious quality/placement/suitability.
Two examples:
-The sensors Intel uses in their cores are intended only to be accurate as thermal shutdown approaches. Intel could care less if the sensor gives accurate data at idle/normal load levels.
Three of the four sensors in my quad core don't even move below @45-50°C, they are useless for checking temp normally.
http://img.photobucket.com/albums/v78/clocker/Currenttemp.png

-Temp sensors for many hard drives are just chips on the circuit board- nowhere near the heat generating drive motor.
You can aim a small useless fan at the circuit board and watch the reported temp plummet, even though the drive case itself remains very hot.

The reality is that you're inferring operating temps and the only real hard parameter you can embrace is thermal shutdown.
If it runs, your cooling is fine, if it throttles/shuts off, it's not.

Your project will be much easier if you eschew the term "silent" and embrace "not irritating".
Rather than striving for zero noise, seek instead noise that's either below the room ambient or at least not distracting.
All fans make sound but large, slow moving fans are easier to live with.
Any grill/mesh/dust filter will increase fan noise...ditch 'em and live with the dust or keep them and accept the (small) penalty.

I do not buy into the "case airflow" theory...the idea that fans on the front/back/top somehow magically create air currents that seek out hot spots and then carry away heat.
Bullshit.
If you're gonna use a fan (and you will), deploy it as directly to the heatsource as possible and ignore where the air is coming from or going..it'll take care of itself.

Pay attention to fan specs, there are lots of fans and some manufacturers pay more attention to noise than others.
Blade and casing design both play a part but essentially you're balancing airflow against noise output...more air=more noise.
A good fan controller is a must because once you decide on the fans, any further experiments will require speeding up or slowing them down to hit the sweet spot between too loud and too hot.

Your case is also a big part of the equation.
I've seen Zalman and Silverstone home theater cases that are basically just slabs of aluminum and they muffle internal sound much better than a standard stamped steel case.
They don't rattle, either.

Neve, there are lots of pretty good solutions available to you, there's no need to reinvent this particular wheel by custom building heatpipe contraptions.

[zot]

On many PCs the power supply can make as much (or more) noise as the processor fan. Being a niche market, passively-cooled PSUs are not cheap. But it doesn't end there. Another factor to consider is that without a PSU fan exhausting the hot case air, there needs to be much more passive case ventilation, and since most cases were designed for fans, that typically means running it with the side panel removed.

Because it's a lot of work and expense putting together a nearly-silent desktop PC, a much simpler and cheaper solution for the noise-averse might be to just use a laptop -- as most run very quiet out of the box.